An uninterruptible power supply (UPS) is used to provide backup power to an electrical device, or load, when the primary power source, or mains, fails. Typical loads include computer systems, but other loads, such as heating/cooling/ventilation systems, lighting systems, network switches and routers, and security and data center management systems may also be powered by a UPS. A UPS designed for data center or industrial use may provide backup power for loads for several hours.
A UPS unit typically includes a logic power supply (LPS) and one or more batteries. The LPS is designed to receive power from the batteries or from a battery charger. Additionally, the batteries act as a power source when AC mains power is unavailable. The battery charger, which converts AC power to DC power, may be included in the UPS to charge the batteries when AC mains is available to ensure that backup power will be available when needed. The UPS may also include a control unit for automatically managing the operation of the UPS and the power conversion functions.